1. Field of the Invention
This invention relates to an infrared radiation sensor for noncontact measurement of the temperature of an object under test such as tymponic membrane, and a method for the production thereof.
2. Description of the Prior Art
Recently, various techniques have-been developed for the production of infrared radiation sensors advantageously used such as for noncontact type thermometers by using the technique for fine processing of semiconductors. The infrared sensor has a construction completed by forming a micro bridge portion formed on a sensor substrate and further forming an infrared radiation sensing portion on the bridge portion. The bridge structure which has the thermosensitive portion of device suspended is after the fashion of a bridge above the supporting substrate is intended to improve the sensitivity of response of the device.
The infrared radiation sensing portions which are used in the infrared sensors may be classified into those of the bolometer type having the resistance of a device varied proportionately to a change caused in the sensor temperature by infrared radiation, those of the thermopile type having the electromotive force of a device varied similarly, and those of the pyroelectric type having the electromotive force of a device varied proportionately to a change in the dose of infrared radiation. The infrared radiation sensing portions of the bolometer type, among other types, allow miniaturization of their sensors as because they are capable of directly indicating temperature from the magnitude of resistance. The infrared radiation sensor of the bolometer type is generally provided with at least two infrared radiation sensing portions, one of which is adapted to admit infrared radiation and the other shielded from infrared radiation. By deriving a differential output between the infrared sensing portion admitting the infrared radiation and the infrared radiation sensing portion repelling the infrared radiation, this sensor is enabled to detect accurately the net dose of infrared radiation free from electrical noise and thermal disturbance.
Incidentally, the conventional infrared radiation sensor has these at least two infrared sensing portions formed on only one of the opposite surfaces of a semiconductor wafer or substrate which serves as the sensor substrate.
Since the conventional infrared radiation sensor has at least two infrared sensing portions formed only on one of the opposite surfaces of the sensor substrate, it is difficult to allow the infrared radiation to impinge solely on one of the infrared sensing portions and prevent it from impinging on the other infrared radiation sensing portion. From the differential outputs of these two infrared radiation sensing portions, therefore, the net dose of impinging infrared radiation cannot be accurately detected. The data of determination consequently obtained must be subjected to various corrections. Further, the conventional infrared radiation sensor has a limit to the overall miniaturization thereof because of the fact that two or more infrared radiation sensing portions are formed on one and the same surface of the sensor substrate, coupled with the problem of shielding against the infrared radiation.
An object of this invention therefore, is to provide a novel infrared radiation sensor and a method for the production thereof.
Another object of this invention is to provide an infrared radiation sensor which allows generous overall miniaturization thereof, enables the infrared radiation to impinge infallibly on a specific infrared radiation sensing portion exclusively, and warrants accurate detection of the dose of infrared radiation and a method for the production of the infrared radiation sensor.